Constraining the properties of K_{l3} form factors with analyticity and unitarity

Abstract

Bounds on the shape parameters of K_{l3} form factors are investigated in a general model independent framework. Using the method of unitarity bounds for correlators evaluated in pQCD, chiral symmetry and experimental information on the phase and modulus of \pi K form factors up to an energy t_{in}=1 GeV^2, we constrain the shape parameters of the scalar and vector form factors, the value of the scalar form factor at t=M_\pi^2-M_K^2, and exclude regions where zeros can exist on the real energy line and in the complex energy plane.

Comments: 8 pages latex, PoS style files, talk given at RADCOR 2011, Mamallapuram, India, 26 - 30 September, 2011; replaced with v2 which corrects typographical error in one of the author's names and eliminates 2 other minor typographical errors